motor starting current with NI9505

[Ricky1]

Hi!

I want to control a motor (see Attachment-Product 148867) with the Module NI9505. Now I don't know if the module 9505 can support this kind of motor. I can't really understand the concept of starting current, so I don't know if the module 9505 can supply enough current to start the motor.

can anyone help me?

Thanks

Ricky

[Jochen]

Hi Ricky,

I have just recently used this exact motor type in combination with the 9505 in a student project about mobile robotics (click here to see the motors/robots in action). We have used the motors with a 74:1 gearing ratio. I have been very satsified with the performance of the motors. Still to maximize the torque you should consider using NI 9931 high power connector terminals.

Kind regards,

Jochen Klier

National Instruments

[AlexxxR]

Hi Ricky,

the NI-9505 is able to handle motors with up to 60W. If you want to drive Motors with more power you can use the NI-9931. This HW-Addon is quite new but it in Combination to the NI-9505 it can drive Motors with up to 7.3A. That`s enough for yours. The other point you have to consider is the voltage, because the RE-40 has the possibility of different windings you have to choose your voltage. The NI-9505 as I know kan handle up to 30V.

Another possibilty you can use is a combination of a standard Analog Out Module and a Digital In, then you can control the Amplifier from maxon, this gives you some more degrees of freedom, for example you can use EC-Drives or DC-Drives and a Motor with 48V or something like that.

Best regards

Alex Rudolph

Technical Support

NI Switzerland

[Ricky1]

Thank you a lot Mr. Klier and Mr.Rudolph! These are nice answers for me! 😃

Yes I already ordered the NI9931 to improve the efficiency of the NI9505.

Just a question:

The NI9505 can supply up to 12A peak. The maximal starting current of the motor (148867) is 75.7A. This should play a role, isn't it? My starting current is dependent of the load I have (160mNm)..

Thank you!

Ricky

[Jochen]

The starting current is the maximum current that the motor could draw phyiscally. It doesn't mean, that this amount of current is required to start the motor. If the drive limits the maximum current, the motor can't draw more current than provided by the drive.

Jochen

[Jochen]

The starting current is the maximum current that the motor could draw phyiscally. It doesn't mean, that this amount of current is required to start the motor. If the drive limits the maximum current, the motor can't draw more current than provided by the drive.

Jochen

[Jochen]

The starting current is the maximum current that the motor could draw phyiscally. It doesn't mean, that this amount of current is required to start the motor. If the drive limits the maximum current, the motor can't draw more current than provided by the drive..

Jochen

[Jochen]

Sorry for the post flooding. It looks like something went wrong with the forums (I have received multiple timeout and error messages)...

[Ricky1]

The motor must drive a maximal load of 10-20Kg (direct drive->no gear).

With a lower starting current, will the motor slower accelerate? I must achieve an acceleration of 4800rad/s^2.

Thanks for your time!

Best regards

Ricky

[Jochen]

Without knowing the dimensions of your load, the sheer mass of your load doesn't provide enough information about your load's inertia. But as long as your load is not just a long beam, the inertia of your load is probably significantly higher than the inertia of your motor's rotor and that's where the problem starts.

Do you know what happens, if you try to accelerate a billard ball by shooting with a marble on it? Even if the marble has enough kinetic energy to accelerate the billard ball to the desired speed, it can't transfer this energy to the billard ball. The marble bounces back, keeping most of it's energy. The same thing is true for the relationship of motors and loads. So even if you would use a much stronger drive, you probably won't be able to transfer the motor's power to the load. Instead you will see torque reflections causing oscillations and reduced acceleration. Thus I strongly recommend using a gearbox!

Regards,

Jochen

P. S.: Some more information about starting current: This is the current a stopped motor draws for a very short time if you turn on a power supply without current limiting. In this situation the motor accelerates at it' maximum pace but without any type of control. This is not a realistic situation for a DC motor in closed loop control and typically drives can't drive such an amount of current - and there is also no need for this.